In industrial processes it is to-day often desirable at various stages of the material handling to be able to obtain quick information regarding the concentration of various components forming part of the material, which is carried through the process in limited quantities, for instance in cars or in ships, or which moves on conveyors, in transportation ducts or the like.
Investigations have disclosed that it is possible to expose a material to neutron irradiation in order to obtain a prompt emission of gamma rays from components in the material, said gamma radiation being characteristic of the irradiated component and being also related in a certain way to the concentration of said component in the material. It is then possible firstly to produce a reference diagram by carrying out a number of measurements of the gamma radiation which is typical for the component in question at various concentrations of said component. The said reference diagram may then be utilized as a calibrating diagram for the practical measurements in question. Such a diagram for measuring the concentration of iron in a certain ore may as an example have the form illustrated in the sketch A below. ##STR1##
Prior experiments using a .sup.239 Pu-Be radiation source and a scintillation detector have not given sufficiently accurate results and have proved to be much too dependent on the composition of the material and on its shape. Furthermore, in the known apparatuses too little consideration has been given to the practical conditions and the safety precautions against radiation hazards.